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MSGEQ7-Based DIY Audio Spectrum Analyzer: Construction

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Max The Magnificent
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Re: Timings
Max The Magnificent   7/14/2014 11:29:47 AM
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@David: Have you factored you're ADC conversion time into this?

I checked this the old-fashioned way on a scope -- check out my next blog which will be on the test procedures I used.

David Ashton
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Re: Timings
David Ashton   7/12/2014 7:54:57 PM
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@Max....well you have proved that the above works and you have exceeded the minimum strobe to strobe time.  Have you factored youre ADC conversion time into this?  (Is it fixed or variable?) Without knowing the specs for the minimum strobe high time you may be wasting time that might be precious later when your design gets more advanced.   I may be being pedantic here but I'm sure you could find any number of readers here who've come unstuck by NOT being pedantic about timings... :-) 

Max The Magnificent
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Re: Timings
Max The Magnificent   7/12/2014 2:00:50 PM
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@David: maybe we could get a gig compiling data sheets for MSI :-)

Stranger things have happened -- I've created data sheets before -- I pride myself on my waveform diagrams LOL

Max The Magnificent
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Re: Timings
Max The Magnificent   7/12/2014 1:59:27 PM
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@David: But the minimum strobe high time is not given...

I'm simply making the strobe go low -- waiting 40us (a bit more than the specified minimum of 36us), reading the data, making the  strobe go high, and waiting another 40us, giving a strobe-to-strobe period of 80+us (which is bigger than the specified minimum of 72us)...

David Ashton
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Re: Timings
David Ashton   7/12/2014 4:07:13 AM
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@Max - maybe we could get a gig compiling data sheets for MSI :-)

David Ashton
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Re: Timings
David Ashton   7/11/2014 9:14:29 PM
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@Max...well I certainly stirred up a hornet's nest there, didn't I? :-)

That makes a lot more sense.  You can't read the data while the strobe is high but you can extend the strobe low as long as you want or need, as long as you wait the 36us for the data to settle...  But the minimum strobe high time is not given, maybe that is the 18 us?   It would be important to know that if you were using a fast MCU and giving a strobe high pulse at the end of your ADC conversion.  Could MSI confirm that?

Max The Magnificent
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Re: Timings
Max The Magnificent   7/11/2014 5:32:26 PM
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@David: I notice the minimum strobe pulse width is less (18us) than the settling time (36us) - which implies you can read the data even if the strobe has gone back high? (ie you could actually read data during the purple times in your diagram?)


Hi David -- based on your question -- and on the fact that it wasn't possible to say one way or the other from the existing datasheet -- I contacted the folks who make the MSGEQ7. They gave me a lot of information, which I've reflected back into the main column above. But the bottom line is that the waveform diagram shoudl actually look like the following:



David Ashton
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Re: Resistor value tools
David Ashton   7/10/2014 4:19:52 PM
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@Antedeluvian - as well as this, I have very rarely seen an extra band on a resistor to indicate temperature coefficient, and in the old days they used to put a pink band on to indicate high stability.     Fortunately I don't move in such esoteric circles and for what I need E12 values are usually fine....

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Re: Resistor value tools
David Ashton   7/10/2014 4:16:20 PM
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@Max...I am a card-carrying member of Scroungers Of Boards (SOB :-)

antedeluvian
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Re: Resistor value tools
antedeluvian   7/10/2014 12:09:03 PM
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David

I guess there is a good reason for this - for (say) LED dropping resistors or pull-up resistors (which covers a good deal of what resistors are used for theses days) the exact value is not critical at all, so by sticking to E12 values

There may be a bit more. A 681R 1% resistor is the same as a 680R 5% resistor if you up the wattage rating. As an example, in the same package the 1% is rated at 1/4W and the 5% as 1/2W. As a boss of mine used to say, when it comes to power dissipation there is no magic so why the power rating difference (actually there is a bit more to that as well- maybe the subject of a future blog)? The real difference is that if you allow the 1% to warm up the resistance will drift out beyond the 1% limit. When it comes to LEDs there is a good probability that the current you are driving them with will warm up the resistor, but for an LED as you point out, who cares?

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